What has emerged in nature in the course of evolution can now be used to break new ground in architecture thanks to computer-based simulations and manufacturing techniques. As part of a transregional collaborative research centre, German researchers have started to use this bionics approach to explore new designs and functional innovations.
Prof. Dr.-Ing. Jan Knippers is head of the Institute of Building Structures and Structural Design (ITKE) at the University of Stuttgart and spokesperson of the DFG-funded transregional collaborative research centre TRR 141 “Biological Design and Integrative Structures – Analysis, Simulation and Implementation in Architecture”. The Universities of Tübingen and Freiburg as well as the Fraunhofer Institute for Building Physics (IBP) in Stuttgart are also involved in the TRR 141 research centre. When researchers from Stuttgart start thinking about implementing biological principles in the field of architecture, the name that usually crops up is that of Frei Otto. Otto taught at the University of Stuttgart and, along with a group of architects and engineers led by Günter Behnisch and Fritz Leonhardt, designed the roof of the Olympic Stadium in Munich for the 1972 Summer Olympics.
Knippers now wants to take Otto's work and, rather than continuing where Otto left off, steer it in new directions. Knippers is basing his plans on the enormous advances made in molecular biology, the material sciences and simulation sciences in recent years. “In terms of abstract basic research, Otto's work centred on principal questions. Nowadays, computer-based modelling and manufacturing processes have opened up totally new possibilities, with simulations playing a crucial role in today’s technology. They help us to copy biological principles and create technical models. They also enable us to perform in-depth analyses of biological structures,” says Knippers.
Knippers cites his long-standing and successful cooperation with a group of botanists led by Prof. Dr. Thomas Speck at the University of Freiburg as a key starting point for the new research network. “We have been studying elastic plant movements and using them as role models for designing new lightweight structures. Our research has produced Flectofin, a shading system of hingeless vertical lamellas inspired by the deformation principle found in Strelitzia, the bird-of-paradise flower. It's a robust mechanism of lamellas deployed without hinges that can easily be adapted to different types of construction, including bent glass facades. The principle of initiating movement through elasticity has attracted a lot of attention that has helped us advance the project considerably,” says Knippers.
Flectofin is an excellent example of the researchers’ interdisciplinary approach, which has made good use of progress in both construction engineering, and the material sciences: the system is based on an elastic polymer processed into a fibre composite lamella. The team, also involving researchers from the ITV Denkendorf, has been awarded the “Techtextil Innovation Award – Architecture” and the Schauenburg Foundation's highly endowed “International Bionic Award”.
The collaborative research centre now wants to build on these successes. A key factor in the success is the cooperation with researchers from the Simulation Technology excellence cluster (SimTech) at the University of Stuttgart. No less than five SimTech project leaders play a part in modelling biological principles and developing construction principles that can also be used by architects and construction engineers. “We are moving from biology to engineering, and developing models that can simulate the load capacity or mobility of plant parts, according to requirements,” says Knippers. Knippers and his colleagues build their constructions and designs based on the simulation results. In terms of movement, the researchers are also looking into the folding mechanism of the Venus flytrap that closes when an insect strikes the hairs of the inner trap surface. Plants like Schefflera or Dracaena have an even more impressive structure. Their branching systems could potentially be used as models for novel support structures. “Studying the fibre orientation in Schefflera plants will help us to improve the structural integrity of buildings,” says Knippers.
The collaborative research centre is inspired by animals as well as plants. The team led by Prof. Dr. Oliver Betz at the University of Tübingen is exploring the stinging and sucking mouth parts of the kissing bug Dipetalogaster maxima for their suitability as models for toothed elements with adaptive stiffness. The researchers are also fascinated by the carrying capacity of the sea urchin shell. Knippers uses the sea urchin shell to explain how the researchers in the collaborative research centre work: “We use imaging methods and material tests to find out the direction of the forces in the joints of the sea urchin shell. All the data is then combined and used to develop a mechanical model, which then serves as the basis for simulations.”
The simulations are also used for up- or downscaling. It is difficult to transfer small plant and animal structures to a larger scale on a one-to-one basis, as factors that are insignificant on a small scale (physical parameters such as wind and temperature) might become important on the larger scale. Therefore, the collaborative research centre will focus on developing simulations in which all influences will be effectively taken into account to make up-scaling work both geometrically and statistically successful.
A separate project area has been created to explore possibilities and feasibility limits in which interdisciplinary teams develop methods for the biomimetic transfer of results into the various fields of application. Another subproject focuses on developing interdisciplinary standards for communication and sustainability assessment in bionics research and is aimed at making the methods fundamentally and sustainably usable. The researchers always bear in mind how research as a whole can benefit from their findings. “The simulation of biological role models provides us with interesting findings for constructions as well as provoking new questions of interest for basic scientific research,” says Knippers citing the Venus flytrap as an example. “The analysis of how Venus flytraps open and close has given biologists food for thought: which morphological properties are responsible for the different closing behaviours of Venus flytrap subspecies?”